Aaaargh - hearing loops

[grapevinebass]

Took my new wonderful new bass with top notch active pickups to play in church band rehearsal this weekend. Practice completely disrupted by squawks and feedback from the sound system. Very puzzled that turning down, and even unplugging the bass made little difference. Eventually worked out it was due to the hearing loop.

It took me back to a gig a couple of years ago at a conference venue, when sound in rehearsal was dire. Then the lead guitarist riffs started coming out of the rhythm guitarists back line amp! Yes - it was the hearing loop, and we had to dismantle the sound desk to get to disconnect it. Lost most of our set up time and sound check - result was a very poor gig.

So this time I had to swap my bass to one with less sensitive pickups, and stand right at the back of the stage and just about got away with it.

I hate hearing loops! Are there gadgets to get round this problem? The church sound engineer said that wrapping the bass in kitchen foil solves the problem, but I felt this was not helpful.

[JTUK]

What was the desk..??

[JapanAxe]

[quote name='grapevinebass' timestamp='1424628125' post='2698478']
Took my new wonderful new bass with top notch active pickups to play in church band rehearsal this weekend. Practice completely disrupted by squawks and feedback from the sound system. Very puzzled that turning down, and even unplugging the bass made little difference. Eventually worked out it was due to the hearing loop.

It took me back to a gig a couple of years ago at a conference venue, when sound in rehearsal was dire. Then the lead guitarist riffs started coming out of the rhythm guitarists back line amp! Yes - it was the hearing loop, and we had to dismantle the sound desk to get to disconnect it. Lost most of our set up time and sound check - result was a very poor gig.

So this time I had to swap my bass to one with less sensitive pickups, and stand right at the back of the stage and just about got away with it.

I hate hearing loops! Are there gadgets to get round this problem? The church sound engineer said that wrapping the bass in kitchen foil solves the problem, but I felt this was not helpful.
[/quote]

Don't forget your tinfoil hat! But seriously, the signal from an inductance loop will find its way into anything that isn't hum-cancelling.

[Len_derby]

Sorry if this sounds negative, but we have exactly the same problem in my church band and we've never found a solution apart from switching off the hearing loop during songs. The induction loop system does look like it's pretty old, so it is possible newer equipment may be more tolerant.

[James Nada]

I don't think the problem occurs with Piezo pickups, so you could use an electro-acoustic basss. If you're happy with that solution you could then look into "normal" basses with piezo pickups.

As for any guitarists in your band, same solution, but they'll need far more convincing than us pragmatic bassists.

[subrob]

What you're experiencing is an electromagnetic feedback loop. An inductive loop system is intended to take an audio feed and fill the room with it. A hearing aid has a 'T' position for use with a phone. In brief, it's a small coil of wire, designed to induce electromagnetic current. Where else do we see these coils? Ah yes, wrapped around the pole pieces in our pick ups.

Be alert to any dynamic mic also exhibiting the same behaviour, or (any mic) being the means by which your instrument is interacting with the loop.

It is a feedback loop, so any steps you can take to break it, I.e getting guitars away from the loop routing, should help. If the loop is fed from the main out of a mixer, or fed from the mixer on a basic mixer amp, then breaking the link might be tricky. Turning the loop amp down or off might be the only option. Unless someone has ££s to spend on a newly installed low spill array loop system, and you can get under the church floor to cable it.

[grapevinebass]

Thanks Subrob, very helpful post.

[Jonesthebass]

Hearing aid loops are run off a hearing aid loop amplifier........ In my experience of fitting them in churches might I suggest you simply flick the power switch on the front to off. No need to unplug stuff out of the desk. Just remember to switch it back on once finished over wise we get a call out the week later because the loop amp has stopped working!

[Owen]

We run one in church but have it on a dedicated aux send so only put vox + a bit of keys through it. This sorts out most problems, but there are some guitars it will interfere with come what may.

[gelfin]

I operate the media system in my church and we have had the same problem with certain bits of kit.
It turns out that the loop is pretty old and was installed in such a way as to cover way too big an area.
Luckily I was in a position to install a smaller loop in the basement. Just as in the post above which appeared while I am typing. We / I send the signal to the loop via aux 1
on the mixer and can just shut it off quickly if a problem arises.

Edited February 23, 2015 by gelfin

[mcnach]

We recorded our first album in an old disused church that had been converted into a series of interesting rooms. On one of the sessions we noticed one of the guitar amps producing some strange noises. We turned it up and we could hear... people... it sounded like a cafeteria, with sound of cups and spoons...
We had a break and decided to investigate.
A nearby church was holding a meeting, and we went in and asked... They had their system on. They said they didn't need it on at the time, turned it off, and no more ghosts coming out of the guitar amp.